A metallic ink has gained wide popularity because its written markings have intense metallic glittering effects; so many products concerning the metallic ink have been on the market in recent decades.
The earlier metallic ink generally uses aliphatic hydrocarbons or long-chain organic compounds as its solvent. However, these compounds are mostly derived from fossil fuels, and large quantities of pollutants are generated during its production process and are easy to cause severe pollution of the environment, which is not conducive to energy conservation and environmental protection. Furthermore, the use of organic compounds as solvents could do some harm to human bodies and environments in most cases. For example, in the U.S. Pat. No. 8,846,797 B2, the preferred solvent is naphtha. Although the patent can solve such problem that a metallic ink composition is unable to be stably stored in and be written by a cotton core-type writing instrument for a long time, the naphtha can damage nervous systems of human bodies, and bring health risks to users to a certain extent.
In order to address the problems regarding environmental protection and safety of human bodies, most of the current metallic ink compositions use water as a solvent to dissolve and disperse various components therein to prepare water-based ink compositions, e.g. the water-based metallic ink compositions disclosed by the U.S. Pat. No. 6,099,629, U.S. Pat. No. 6,083,311, U.S. Pat. No. 6,616,741 B1 and the like. Since water-based metallic inks have long drying time and is difficult to achieve the purpose of quick drying in short time, for the writer, such problem as inadvertently polluting writing surfaces may happen during continuous writing. Besides, the following problems can be caused by the use of water as the main solvent of metallic ink compositions, namely the metallic pigments especially aluminum pigments can produce hydrogen gas in aqueous system, which can bring about some dangers during processing and storage of this kind of metallic ink composition and is not conductive to long-distance transportation; At the same time, that the water's surface tension is relatively high may result in that this kinds of inks have bad spreadability on some smooth and clean surfaces, which leads to such problems as shrinkage of borders, shrinkage of cavity and the like and then limits its scope of application.